Using Nanoparticle Coating in Dedicated Digital Image Correlation for Mixed-Mode CTOD Calculation and Crack Growth Estimation

Crack tip opening displacement (CTOD) is an important parameter in fracture mechanics. Experimentally, the parameter is always calculated using a clip gauge in the first mode. However, the method is inappropriate for the second mode or mixed mode. The current study aims to introduce a new method for CTOD calculation using digital image correlation (DIC). The DIC, which is a powerful technique in the calculation of surface displacement and is applied on various scales, is used to calculate displacements around a crack, thereby calculating the CTOD. The main concept of the study is to use nanoparticles to create a speckle pattern with appropriate speckles to focus on the crack tip and calculate the crack tip displacements. Displacements around cracks are determined by the introduced method, and the capability of the method in the calculation of the CTOD in mixed-mode is proved. Moreover, the crack tip zone and its growth can be determinable.